Panel saw machines of known type are used to cut a single panel or two or more panels both lengthways and crossways. The panels vary in size and are usually placed one over the other in normally large stacks whose dimensions depend on the size of the panels made by the basic panel forming machines.
Panel saw machines, in their minimum standard configurations with a single cutting line to which we shall refer in this specification (purely by way of example, without limiting the scope of the invention), basically comprise:
a horizontal work table to support the stacks of panels to be cut;
a unit for picking up the panels and feeding them, along an axis X (horizontal), towards the end of the table opposite the stack loading end;
a cutting device operative on the part of the panel stack at said end of the work table.
More specifically, the pickup unit comprises a beam equipped with a plurality of clamping elements, for example of the gripper type, located side by side in a direction Y at right angles to the direction of forward or backward feed. The clamping elements act on the rear edge of the panels to be cut and may transport and/or retain (that is, advance or retract) the panels in position while they are being cut and while they are moved backwards and forwards on the work table.
The cutting device (consisting of circular saws and scoring blades) is mounted on a carriage that moves in both directions along the axis Y transversal to the panel feed axis X so as to cut right through all the panels if these are stacked or through only one if a single panel is being processed.
Usually, after the panels have been fed to the cutting line, they are trimmed and then, when necessary, cut one or more times according to a predetermined pattern programmed on the machine.
After the feeding step, if the panels have to be cut first along a direction parallel to the feed direction corresponding to the axis X, the panel stack or the single panel has to be turned through a right angle so that it can be fed to the cutting device in a position appropriate for the programmed pattern.
To facilitate the work of the operators who have to turn the panels downstream of the cutting device, devices such as the one described in patent EP-1.057.599 (in the name of the same Applicant as this invention) have been devised. These devices basically comprise an element for holding down at least one panel being machined and means for turning the panel about the hold-down element.
More specifically, the hold-down element is located in the vicinity of the work table in such a way as to form a pivot in a preset area of the panel and the means for turning the panel about the pivot facilitate panel movement to change the position of the panel relative to the cutting device.
These turning devices, however, have a complex structure including numerous components such as pusher elements associated with the pickup units.
On account of their complexity, the cost of these devices and hence of the machines they are mounted on tend to be quite high.
In particular, when the panel turning means operate in combination with the pickup units, the latter have to be mobile at least transversely along the aforementioned beam, which means that additional components and technology are required, thus further increasing costs.
To overcome these problems, the Applicant developed a different solution for turning the panels (disclosed in patent application WO 2005/042214 by the same Applicant) where an element for holding down the panel or panels (consisting of two mobile plates) is positioned in the vicinity of an edge of the work table and acts on the panels in such a way as to form a pivot and an axis of rotation in a defined area of the panels. There are also power-driven rubber wheels allowing the panel to be rotated about the pivot. The wheels are built into the work table and are mobile between a rest position in which they are away from the panels and a working position in which they are in contact with the panels. This rotation is performed on a multi directional low-friction surface of the work table.
This solution, which is more practical and economical than the solution preceding it is not, however, free of disadvantages, due to the fact that:
in some cases, the panels being rotated may need to be accompanied by the operator (manually or using additional equipment), thus slowing down work and creating dangerous situations for the operator;
when working with panels having smooth, low-friction surfaces, the pivot plates cannot grip the panels firmly enough to keep the stack properly in place, especially at the start or end of a movement, that is to say, during the transition from one state to another.
The aim of this invention is to overcome these disadvantages by providing a panel saw machine that is at once practical and inexpensive and that combines high productivity and panel cutting precision with safe and easy panel rotating operations.